Francois Botha claim that mighty mo hit alot harder than Lewis and Tyson

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The dude punches harder than any heavyweight in history .

I am not an expert on Mighty Mo, but having seen the clip shown above (and only on that evidence), I reckon Earnie Shavers, George Foreman and Sonny Liston - to name but a few - would have been able to dispute this with some pretty powerful evidence of their own?